Vacuum switch drive mechanism

ABSTRACT

Drive mechanism for opening and closing the contacts of a vacuum switch. The mechanism includes a movable cylinder containing coil springs and a movable piston. The piston is connected to the vacuum switch and includes latching means which may be positioned to prevent movement of the pistons relative to the vacuum switch. A spring is compressed between the piston and the cylinder as the cylinder moves in the closing direction. The latching means is then unlatched and the piston is quickly moved by the force of the compressed spring to close the vacuum switch. Another spring is compressed when the cylinder moves in the opening direction. The latching means is then unlatched and the piston is quickly moved against the end of a shaft which is connected to the vacuum switch to open the vacuum switch.

United States Patent 119'] Guidosh 1 VACUUM SWITCH DRIVE MECHANISM Edward F. Guidosh, Hubbard, Ohio [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: Jan. 9, 1973 [21] Appl. N0.:,322,236

[75] lnventor:

[52] US. Cl. 200/144 B, 200/78, 200/153 K,

[451 May 14,1974

Primary Examiner-Robert S. Macon Attorney, Agent, or Firm-J. R. Hanway 5 7 ABSTRACT Drive mechanism for opening and closing the contacts of a vacuum switch. The mechanism includes a movable cylinder containing coil springs and a movable piston. The piston is connected to the vacuum switch and includes latching means which may be positioned to prevent movement of the pistons relative to the vacuum switch. A spring is compressed between the piston and the cylinder as the cylinder moves in the closing direction. The latching means is then unlatched and the piston is quickly moved by the force of the compressed spring to close the vacuum switch. Another spring is compressed when the cylinder moves in the opening direction. The latching means is then unlatched and the piston is quickly moved against the end of a shaft which is connected to the vacuum switch toopen the vacuum switch.

12 Claims, 7 Drawing Figures PATENTEUHAY 14 1914 sum 1 or 4 LOAD 32 TRANSFER SWITCH 34 SELECTOR SWITCH FIG. I

1 VACUUM SWITCH DRIVE MECHANISM BACKGROUND OF THE INVENTION mechanisms for tap changer vacuum switches.

2. Description of the Prior Art Tap changing equipment capable of changing taps while the tapped apparatus is conducting current generally includes one or more switches which divert the load current during the tap changing process. In highvoltage, high-current apparatus, vacuum switches are used because of their ability to interrupt and divert current'without significant arcing. I

Most tap changers which use vacuum switch current interrupters follow a predetermined switching and tap selecting sequence when making a tap change. Normally, the vacuum switch contacts are opened and closed by a mechanism driven by and timed with other drive mechanisms, such as the selector switch drive mechanism. Since vacuum switches must be opened and closed in a manner different than other switches of the tap. changer, a separate drive mechanism for the vacuum switch contacts is required. Therefore, it is desirable, and it is an object of this invention, to provide a vacuum switch drive mechanism whicheconomically and reliably produces the desired vacuum switch contact moving action.

Tap changing apparatus using vacuum switches is'described in U.S. Pat. Nos. 3,764,891 and 3,783,206, Ser. Nos. 269,361 and 269,364, which are both assigned to the same assignee as is this invention. In the apparatus described therein, and in similar apparatus, it is desirable for the vacuum switch drive mechanism to close the vacuum switch contactsquickly, to maintain sufficient force between the contacts, and to open the contacts quickly with sufficient force to separate partially welded contacts. These desired motions must be obtained from a relatively constant speed drive memher which is normally motor'driven. Therefore, it is desirable, and it is another object of this invention, to provide a vacuum switch drive mechanism which converts substantially constant motion into properly timed abrupt. motion of sufficient strength to open and close thevacuum switch contacts properly.

SUMMARY OF THE INVENTION There is disclosed herein a new and useful vacuum switch drive mechanism which properly opens and closes the contacts of the vacuum switch. The vacuum switch drive mechanism includes a cylinder slidably mounted to a stationary member. The cylinder moves in a first direction when opening the vacuum switch contacts andin a second direction when closing the contacts.

A piston is slidably positioned within the cylinder and is attached to a latching device which may be positioned to prevent movement of the piston with respect to the vacuum switch. When the cylinder moves in the second direction, a coil spring is compressed between one end of the cylinder and the piston. When the coil spring has been compressed sufficiently, the latching device is disengaged .by a plate attached to the moving cylinder. This allows the piston to be moved quickly by the spring force. The piston is connected, through shock-absorbing means, to a contact of the vacuum switch. Thus, when the piston moves in the second direction, the contacts of the vacuum switch are closed.

-When the cylinder moves in the first direction, another spring is compressed between the piston and the other end of the cylinder. When this spring has been compressed sufficiently, the latching device is disengaged by the plate attached to the cylinder. This allows the piston to move quickly and strike the head end of a shaft which is effectively attached to a contact of the vacuum switch. Thus, the contacts are abruptly movedapart and the vacuum switch is opened.

BRIEF DESCRIPTION OF THE DRAWING Further advantages and uses of this invention will become more apparent when considered in view of the following detailed description and drawing, in which:

FIG. 1 is a schematic diagram ofa load tap changer;

FIG. 2 is an elevational view, partly in section, of a vacuum switch drive mechanism shown in the fully closed position;

FIG. 3 is a sectional view taken along the line llllll of FIG. 2;

FIG. 4 is an elevational view, partly in section, of a vacuum switch drive mechanism shown in the fully open position;

FIG. 5 is an elevational view, partly in section, of a vacuum switch drive mechanism shown in an open position during the closing sequence;

FIG. 6 is an elevational view, partly in section of a vacuum switch drive mechanism shown in another open position during the closing sequence; and

FIG. 7 is an elevational. view, partly in section, of a vacuum switch drive mechanism shown in a closed position during the opening sequence.

DESCRIPTION OF THE PREFERRED EMBODIMENTS winding 16 includes the taps 18, 20, 22 and 24. The selector switch 26 includes movable contacts 28 and 30 which may be moved to contact different winding taps. The transfer switch 32 connects the movable contacts of the selector switch 26 to the load 34. When changing the load current from one of the selector switch contacts 28 and 30 to the other contact, the transfer switch 32interrupts the load current by opening one or more vacuum switches. The vacuum switch contacts are moved in the proper sequence with the contacts 28 and '30 on the selector switch 26.

FIG. 2 is a view illustrating a drive mechanism constructed according to this invention which may be used to properly move the vacuum switch contacts. The stationary support 36 provides a member for mounting the drive mechanism to a fixed surface of the tap changing apparatus. The housing 38 is attached to the stationary support 36 by the bolts 40 and 42. Rollers 44 and 46 are attached to the bolts 40 and 42, respectively, and

guide the slide 48 which is movable in a direction perpendicular to the plane of FIG. 2.

A driving arm 50 is attached to the slide 48 and furnishes the primary moving force to the vacuum switch drive mechanism. Normally, the motion of the driving arm 50 is derived from and is in sequence with the same mechanism which drives the selector switch 26. Slide 48 co'ntains'a slot 52 into which the cam follower 54 is positioned. As the slide 48 moves in a reciprocating manner, the cam follower 54 follows the contour of the slot 52. The cam follower 54 moves in a first direction 56 to a maximum position 58 and in a second direction 60 to a maximum position 62, using one side of the cam follower 54 as a reference in defining the maximum positions.

The housing 38 supports guides 64- and 66 which are attached to the housing 38 by the bolts 68. A slidable cylinder 70 is positioned between the guides 64 and 66 and are guided therein by the bearing surfaces 72 and 74. Although described in the preferred embodiment of this invention as being circularly shaped in crosssection, the cylinder 70 could have other shapes without departing from the scope of the invention.

The cylinder 70 is moved in directions 56 and 60 by an arm 76 which is attached to the cam follower 54. A

more detailed view of the cylinder driving means is shown in FIG. 3. A suitably shaped piston 78 is positioned within and is slidable with respect to the cylinder 70. A projection 80 around the inside wall of the cylinder 70 provides'the surface on which the piston 78 moves.

A slot 82 in the wall of the cylinder 70 allows the latch locking plate 84, which is connected to the piston 78, to extend to the outside of the cylinder 70. The latch locking plate 84 contains notches 88 and 90 which are dimensioned to receive rollers 92 and 94 of the latches 96 and 98, respectively. The latch 96 is pivotable around the shaft 100 and is forced against the latch locking plate 84 by the coil spring 102. The latch 98 is pivotable around the shaft 104 and is forced against the latch locking plate 84 by the coil spring 106.

The latch releasing plate 108 is shown in phantom in FIG. 2 since it is connected to the cylinder 70 at a location which is in front of the plane of FIG. 2. The latches 96 and 98 are engagable with the latch locking plate 84 to lock the piston 78 in a particular position with respect to the stationary housing 38. The latch releasing plate 108 is positioned to disengage the latches 96 and 98 when the cylinder 70 is moved to particular locations.

The cylinder 70 encloses several components, including the piston 78, which cooperate to produce the desired control of the vacuum switch contacts 110 and 112. A coil spring 114 is compressed between a ring 116 which is fixed to the cylinder 70 and a ring 118 which is slidable within the cylinder 70. A coil spring 120 is compressed between rings 122 and 124 which are both slidable within the cylinder 70. Ring 126 limits the distance which the ring 124 may slide within the cylinder 70.

A bolt 129 and a bushing 131 form a shaft which is slidably positioned through an opening 132 in the piston 78 and is attached to a piston or coupler 134 which is connected to-the vacuum switch contact 110. The piston 78 includes a cavity 136 at one end thereof into which a portion of the tubular member 138 is placed.

The tubular member 138 extends around the shaft 130 and is slidable thereon. A coil spring 140 is compressed between the piston 78 and the tubular member 138.

FIG. 3 illustrates some of the components of the vacuum switch drive mechanism with greater clarity than shown in FIG. 2. When the slide 48 moves, the arm 76 rotates the shaft which is secured by the bearings 152 and 154. As the shaft 150 rotates, the arm 156 swings and slides the cylinder 70 with the force provided through the pivotable coupling 158. The latch releasing plate 108 is connected to the cylinder 70 and is aligned with the roller 160 which is rigidly attached to the latch 98. Latch 96 shown in FIG. 2 also includes another roller which is aligned with the latch releasing plate 108.

The operation of the vacuum switch drive mechanism will be described first with the aid of FIG. 4. In FIG. 4, the vacuum switch contacts are fully open as indicated by the fact that the coupler 134 is positioned against the housing 38. Thecam follower 54 is located at position 58 which corresponds to the maximum deflection of the cylinder 70 in direction 56. The piston 78 is also at its maximum deflection in the direction 56, with respect to the stationary housing 38, and is locked in this position by the latch 98 which is engaged with the locking plate 84. Therefore, the vacuum switch contacs are locked open in this position.

In FIG. 5, the slide 48 has moved sufficiently to move the cam follower 54 in direction 60. This corresponds to the beginning of the vacuum switch closing sequence. As the cam follower 54 moves in direction 60, the cylinder 70 moves in the same direction. However, piston 78 remains stationary with respect to the housing 38 because it is locked in position by latch 98. Compression of the spring 120 is reduced and the latch releasing plate 108 is moved to the position shown.

FIG. 6 illustrates the vacuum switch drive mechanism after further movement of the slide 48. The cam follower 54 has increased the movement of the cylinder 70 in direction 60. The piston 78 still has not moved since it is still locked in position by latch 98. The compression of spring 114 is increased since the ring 118 has been moved, with respect to the cylinder 70, by the piston 78. The releasing plate 108 is in a position in which further movement of the cylinder 70 will disengage the latch 98 and allow the piston 78 to move in the direction 60 due to the force of the spring 114.

.Further movement in direction 60 of the cylinder 70 from the position indicated in FIG. 6 causes the latch 98 to disengage from the plate 84 since the latch 98 is pushed downward by the plate 108. The force of the compressed spring 114 quickly moves the piston 78 in the direction 60. The shaft 130 slides through the piston 78 and does not significantly help in pushing the coupler 134 away from the housing 38. FIG. 2 illustrates the vacuum switch drive mechanism when the vacuum switch contacts are closed.

The tubular member 138 is pushed in the direction 60 as the piston 78 moves in the direction 60. The tubular member 138 pushes the coupler 134 which pushes the contact 110 against the contact 112. The spring 140 and oil contained within the tubular member 138 provide the necessary connection between the tubular member 138 and the piston 78.

When the contacts 110 and 112 are forced together, an override feature of the invention is provided by the telescoping of the tubular member 138 into the piston cavity 136. The oil and the spring 140 contained within the tubularmember 138 dampen the linear motion of the coupler 134 and help prevent bouncing of the contact 110 when it hits the contact 112. The velocity of the contact closing may also be controlled by the dash-pot 170. The piston 78 is locked in the closed" position as shown in FIG. 2 by the latch 96.

FIG. 7 illustrates the vacuum switch drive mechanism when the vacuum switch contacts are closed but are about to open. The cam follower 54 and the cylinder 70 have moved in direction 56 from the position shown in FIG. 2. The compression on the spring 120 is increased since the ring 122 is held by the piston 78 and the ring 124 is held by the retaining ring 126.

- When the cylinder 70 moves slightly farther in direction 56, the plate 108 moves latch 96 down and allows piston 78 to move quickly in direction 56 due to the force provided by spring 120. Since thehead 174 of the shaft 130 is positioned away from the piston 78, a hammering or impact contact opening action is obtained which helps to disengage partially welded contacts.

When the cam follower 54 reaches its extreme position in direction 56, the latch 98 locks the piston 78 in position and locks the contacts in an open position. In this condition, the drive mechanism components are positioned as illustrated in FIG. 4. If the force of the spring 120 is insufficient to separate partially welded contacts, a positive follow-through feature is provided by the drive mechanism. The ring 124 would contact the end 176 of the piston 78 and forcibly pull the contacts apart since there would not be any spring action between the cam follower 54 and the shaft 130.

The vacuum switch drive mechanism described herein permits reciprocating motion to be modified for proper vacuum switch control. As the cylinder 70 moves in direction 60, spring force is increased and quickly released to close the contacts. As the cylinder 70 moves in the direction 56, spring force is increased and quickly released to open the contacts.

Since numerous changes may be made in the abovedescribed apparatus and since different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all of the matter contained in the foregoing description; or shown in the accompanying drawing, shall be interpreted as illustrative rather than limiting.

I claim a as invention:

1. A vacuum switch drive mechanism comprising:

a slidable member containing an opening therein;

latch releasing means connected to said slidable member;

means for sliding said slidable member in first and second linear directions;

a piston slidably disposed within the opening in said slidable member;

' latch locking means connected to saidpiston;

first resilient means for forcing said piston in the first linear direction with respect to said slidable member;

secondresilient means for forcing said piston in the second linear direction with respect to said slidable member;

means for connecting said piston to a contact of the vacuum switch;

first latching means which is engagable with said latch locking means to prevent movement of said piston in the first linear direction; and

second latching means which is engagable with said latch locking means to prevent movement of said piston in the second linear direction;

said latch releasing means being positioned so that predetermined movements of said latch releasing means disengage said first and second latching means from said latch locking means to allow movement of said piston.

2. The vacuum switch drive mechanism of claim I wherein the opening in the slidable member is substantially cylindrically shaped and the slidable member contains a slot through which the latch locking means extends.

3. The vacuum switch drive mechanism of claim 2 wherein the opening in said slidable member contains a cylindrical projection which guides the piston within the slidable member.

4. The vacuum switch drive mechanism of claim 1 wherein the latch locking means includes a plate connected to the piston, said plate containing first and second notches dimensioned to permit engagement with the latching means.

5. The vacuum switch drive mechanism of claim 1 wherein the first and second. latching means include first and second pivotable arms, each of said arms including a roller which is forced by resilient means against the latch locking means. 7

6. The vacuum switch drive mechanism of claim 1 wherein the latch releasing means comprises a plate connected to the slidable member, said plate being positioned and dimensioned to disengage the latching means from the latch locking means when the slidable member is in a predetermined position.

7. The vacuum switch drive mechanism of claim I wherein the means for sliding the slidable member in first and second linear directions comprises a movable slide which contains a slot and a cam follower disposed in said slot.

8. The vacuum switch drive mechanism of claim 1 wherein the first resilient means comprises a coil spring having first and second ends disposed within the opening in the slidable member, the first end being positioned against first means fixed to the slidable member, the second end being positioned against second means slidable with respect to the slidable member and dimensioned to contact the piston.

9. The vacuum switch drive mechanism of claim 1 wherein the second resilient means comprises a coil spring having first and second ends disposed within the opening in the slidable member, the first end being positioned against first means slidable with respect to the slidable member and dimensioned to contact the piston, the second end being positioned against second means slidable with respect to the slidable member.

10. The vacuum switch drive mechanism of claim 1 wherein the means for connecting the piston to the vac uum switch contacts comprises a tubular member inserted within a cavity in the piston, a coil spring positioned between said tubular member and the piston, with said tubular member being connected to the vacuum switch.

11. The vacuum switch drive mechanism of claim 10 wherein the means for connecting the piston to the vacuum switch also includes a shaft slidably positioned through an opening in the piston and rigidly connected to the vacuum switch.

12. A vacuum switch drive mechanism comprising:

a slidable cylinder containing an opening therein;

a latch releasing plate connected to said cylinder;

means for moving said cylinder in first and second linear directions;

a piston slidably disposed within the opening in said cylinder;

a latch locking plate connected to said piston and extending through a slot in said cylinder, said latch locking plate containing notches therein;

a first coil spring having first and second ends disposed within the opening in said cylinder, the first end of said first coil spring being positioned against a first ring which is fixed to said cylinder, the second end of said first coil spring being positioned against a second ring which is slidable with respect to said cylinder;

a second coil spring having first and second ends disposed within the opening in said cylinder, the first end of said second coil spring being positioned against a third ring which is slidable with respect to said cylinder, said third ring dimensioned to contact said piston, the second end of said second coil spring being positioned against a fourth ring which is slidable with respect to said cylinder;

a fifth ring fixed to said cylinder at a position which limits the length the fourth ring may slide;

a tubular member positioned within the opening in said cylinder and inserted into a cavity in said piston, said tubular member being connected to a contact of the vacuum switch;

a third coil spring positioned between said tubular member and said piston;

a shaft slidably positioned through an opening in said piston and rigidly connected to the vacuum switch;

ton. 

1. A vacuum switch drive mechanism comprising: a slidable member containing an opening therein; latch releasing means connected to said slidable member; means for sliding said slidable member in first and second linear directions; a piston slidably disposed within the opening in said slidable member; latch locking means connected to said piston; first resilient means for forcing said piston in the first linear direction with respect to said slidable member; second resilient means for forcing said piston in the second linear direction with respect to said slidable member; means for connecting said piston to a contact of the vacuum switch; first latching means which is engagable with said latch locking means to prevent movement of said piston in the first linear direction; and second latching means which is engagable with said latch locking means to prevent movement of said piston in the second linear direction; said latch releasing means being positioned so that predetermined movements of said latch releasing means disengage said first and second latching means from said latch locking means to allow movement of said piston.
 2. The vacuum switch drive mechanism of claim 1 wherein the opening in the slidable member is substantially cylindrically shaped and the slidable member contains a slot through which the latch locking means extends.
 3. The vacuum switch drive mechanism of claim 2 wherein the opening in said slidable member contains a cylindrical projection which guides the piston within the slidable member.
 4. The vacuum switch drive mechanism of claim 1 wherein the latch locking means includes a plate connected to the piston, said plate containing first and second notches dimensioned to permit engagement with the latching means.
 5. The vacuum switch drive mechanism of claim 1 wherein the first and second latching means include first and second pivotable arms, each of said arms including a roller which is forced by resilient means against the latch locking means.
 6. The vacuum switch drive mechanism of claim 1 wherein the latch releasing means comprises a plate connected to the slidable member, said plate being positioned and dimensioned to disengage the latching means from the latch locking means when the slidable member is in a predetermined position.
 7. The vacuum switch drive mechanism of claim 1 wherein the means for sliding the slidable member in first and second linear directions comprises a movable slide which contains a slot and a cam follower disposed in said slot.
 8. The vacuum switch drive mechanism of claim 1 wherein the first resilient means comprises a coil spring having first and second ends disposed within the opening in the slidable member, the first end being positioned against first means fixed to the slidable member, the second end being positioned against second means slidable with respect to the slidable member and dimensioned to contact the piston.
 9. The vacuum switch drive mechanism of claim 1 wherein the second resilient means comprises a coil spring having first and second ends disposed within the opening in the slidable member, the first end being positioned against first means slidable with respect to the slidable member and dimensioned to contact the piston, the second end being positioned against second means slidable with respect to the slidable member.
 10. The vacuum switch drive mechanism of claim 1 wherein the means for connecting the piston to the vacuum switch contacts comprises a tubular member inserted within a cavity in the piston, a coil spring positioned between said tubular member and the piston, with said tubular member being connected to the vacuum switch.
 11. The vacuum switch drive mechanism of claim 10 wherein the means for connecting the piston to the vacuum switch also includes a shaft slidably positioned through an opening in the piston and rigidly connected to the vacuum switch.
 12. A vacuum switch drive mechanism comprising: a slidable cylinder containing an opening therein; a latch releasing plate connected to said cylinder; means for moving said cylinder in first and second linear directions; a piston slidably disposed within the opening in said cylinder; a latch locking plate connected to said piston and extending through a slot in said cylinder, said latch locking plate containing notches therein; a first coil spring having first and second ends disposed within the opening in said cylinder, the first end of said first coil spring being positioned against a first ring which is fixed to said cylinder, the second end of said first coil spring being positioned against a second ring which is slidable with respect to said cylinder; a second coil spring having first and second ends disposed within the opening in said cylinder, the first end of said second coil spring being positioned against a third ring which is slidable with respect to said cylinder, said third ring dimensioned to contact said piston, the second end of said second coil spring being positioned against a fourth ring which is slidable with respect to said cylinder; a fifth ring fixed to said cylinder at a position which limits the length the fourth ring may slide; a tubular member positioned within the opening in said cylinder and inserted into a cavity in said piston, said tubular member being connected to a contact of the vacuum switch; a third coil spring positioned between said tubular member and said piston; a shaft slidably positioned through an opening in said piston and rigidly connected to the vacuum switch; a first latch which is engageable with a notch in said latch locking plate to prevent movement of said piston in the first linear direction; and a second latch which is engageable with a notch in said latch locking plate to prevent movement of said piston in the second linear direction; said latch releasing plate being positioned so that predetermined movements of said latch releasing plate disengage said first and second latches from said latch locking plate to allow movement of said piston. 